1. Field of the Invention
The present invention relates to a method of reading bar codes.
2. Description of the Prior Art
Bar codes in which ID (identification) data are encoded in binary form are used extensively, in most cases attached to an object as black and white binary data corresponding to a merchandise code or the like. These bar codes enable quantities of information to be encoded as combinations of black and white bars which are read by a dedicated scanner.
Thus, such bar codes enable desired ID data to be attached to an object in a form that can be readily decoded and read out as signals that can be processed electrically to provide information such as the content and price. Bar codes can also be utilized for price accounting when the merchandise is sold, and also for inventory control.
In addition to their general use in supplying goods for market distribution, such bar codes are also used extensively in manufacturing for parts control, keeping track of design drawings and, on the clerical side, for controlling accounting chits, for example.
In recent years, bar code readers are being employed that are not restricted to reading simple black and white binary bar codes, but also have multi-tone scanning capabilities that can provide better read precision. In addition to reading bar codes, such multi-tone bar code readers are also capable of reading the contents of drawings and chits; that is, they have OCR (optical character recognition) capabilities hat enable them to recognize shapes and alphanumeric characters, which greatly expand the range of possible applications.
Such a multi-tone OCR reader can be used in combination with a microfilmer. Such a combination converts a scanned drawing or chit to a microfilm in real time while at the same time reading a bar code affixed to the drawing or chit and storing the information as an index identifying the microfilm for search operations.
When an operator reads a bar code manually by pressing a bar code reader against the bar code or by sweeping the reader across the bar code, it is relatively easy for the bar code reader to scan the bar code correctly. However, when a bar code is to be read automatically, a bar code that has not been attached in the correct position on the object can cause a large slope to be produced between the direction in which the bar code is aligned and the direction of the scanning, making it impossible to obtain a correct reading of the data.
Usually bar codes are made relatively wide so that even when such a slope does exist, a complete data reading, that is, one in which the data thus read includes both a start mark and a stop mark, can be obtained with a single sweep of an automatic scanner. If the slope is particularly large, however, the result even of multiple sweeps of the scanner across the width of the bar code can be that none of the sweeps accomplishes a read of the complete data. In such cases, if the bar code cannot be decoded, it can lead to a shut-down of the system.
Especially when a bar code is being decoded automatically by moving the object in a z direction while the bar code is being scanned at right-angles thereto in an x direction, the sequential movement of the bar code along z can carry it beyond the x line of the scanning, again making it impossible to obtain a complete reading of the data.
In the prior art, recovery of the data in such cases has entailed a troublesome procedure usually requiring manual re-entry of the data, such as via a keyboard, for example, which causes problems in fully automated bar code systems.